DDT, one of the most ubiquitous of a class of endocrine disrupting chemicals, has been associated with dramatic adverse effects on the reproductive systems of animals. Effects of DDT in animals and experimental systems are observed at levels in the range of human exposure. Chemicals having endocrine activity similar to DDT are currently in use, and recent studies have suggested male reproductive system disorders are becoming more prevalent. The Investigators propose a nested case-control study of cryptorchidism and hypospadias and in utero exposure to DDT within the Child Health and Development Studies (CHDS) cohort. Such an examination of the role of DDT in the causation of human genital anomalies has not been done previously. The CHDS, a longitudinal study of 20,000 pregnancies among Northern California Kaiser Foundation Health Plan members, enrolled subjects between 1959 and 1966 a time of high domestic use of DDT. All subjects were interviewed during pregnancy about habits and socio-demographic characteristics and almost all children were followed for the first five years of life. The subjects will include 155 male liveborn infants with hypospadias or cryptorchidism and an equal number of randomly selected controls. Levels of DDT and its major metabolites will be assayed from maternal serum currently stored at the National Institutes of Health. The sex steroid hormone, testosterone, and sex hormone binding globulin, possible markers for reproductive system effects of DDT, will be measured from cord blood samples in a subset of 50 infants. The authors hypothesize that maternal DDT levels will be higher in mothers of male with genital anomalies after controlling for confounders. They will examine th effect of DDT on birth weight, gestational age, and steroid hormones as well as the roles these factors may play in the mechanism of DDT's effects. Finding DD to be a risk factor for male genital malformations, would suggest endocrine disrupting chemicals may be significant causes of male reproductive disorders and potentially causes of cancers of the male and female reproductive systems.